<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .parent{
        background: blueviolet;
        display:grid;
        grid-template-columns:auto 1fr;
        grid-gap:20px
    }
    .left{
        width:200px;
        float:left;
        margin-right:20px;
        background: burlywood;
    }
    .right{
        overflow: hidden;
        zoom: 1;
        background: cadetblue;
    }
</style>
<body>
    <div class="parent">
        <div class="left">
            <p>left</p>
        </div>
        <div class="right">
            <p>right</p>
            <p>right</p>
        </div>
    </div>
</body>
</html>